The Skype outage was its first major technical problem since 2007. Photograph: Richard Stonehouse

Internet phone service Skype is facing criticism over its handling of a software failure that brought down connections for millions of consumers and businesses in the US, Europe and Asia.

Skype blamed the problem on the failure of "supernodes", parts of Skype's peer-to-peer network that facilitate calls between users, at about 8.30pm on Wednesday night. When some of those failed, the reminder of the network struggled to cope with traffic that typically handles 25m calls at once.

But Skype was slow to respond to the problem, leaving users in the dark without any updates or advice on the company's official blog, with a minimal message on Twitter that said it was investigating the problem.

A spokesperson dismissed the suggestion that the problem was due to sabotage. "Skype has no evidence to suggest that this was a malicious attack. We've identified a bug in the Skype software which was the root cause of the downtime."

Veteran telecoms blogger Om Malik said the service has become "part of the economic fabric for startups and small businesses around the world", adding that its massive infrastructure should mean it is protected against major outages.

"The outage comes at a time when Skype is starting to ask larger corporations for their business. If I am a big business, I would be extremely cautious about adopting Skype for business, especially in the light of this current outage," said Malik, adding that Skype is keen to attract more lucrative corporate business.

Though Skype was keen to point out that the problem had not affected users of its Skype Connect business product, Malik said the problem demonstrates Skype "is slowly starting to ignore its core and passionate user base who are happy to spend money on its products – consumers and small businesses".

A post by Peter Parkes on Skype's blog said Skype was working to create new "mega-supernodes" to get the system up to speed, and by mid-afternoon today claimed it had recovered to handle around 10m million calls – 40% of its typical capacity.

Skype has built a vast and loyal user base by offering a free basic product that allows users to call each other from anywhere in the world for free. It claims 124 million monthly users as of June 2010, and half a billion registered users.

Its last major outage was in August 2007 when part of a Windows update left some users Skypeless for two days.